BabesiosisDr.Vinaykumar Hallur MBBS, MD(Micro, PGI)

Introduction History

Classification Structure Lifecycle

Epidemiology Pathogenesis Clinical features

Diagnosis Treatment Animal models

Prevention

Introduction Infection due to parasites belonging to genus Babesia

B. microti B. divergens B. duncani WA-1 MO-1 KO -1 EU-1

Obligate intracellular: RBCs Requires both a competent vertebrate and nonvertebrate

host to maintain transmission cycles Transmitted by ixodid ticks to their vertebrate hosts

History

Theobald Smith (July 31, 1859 December 10, 1934) Along with Kilbourne Discovered arthropod borne transmission in 1893 Cattle Febrile heamturia : Bloodied waters of Egypt

History 1957- 1st human case- Yugoslavian farmer 1968- 1st recognized in California (USA) 1976- Ixodes dammini identified as vector for B.

microti 1993- 1st description of WA-1 1996- 1st description of MO-1

Classification Taxonomic Classification phylum Apicomplexa (also called Sporozoa), class Aconoidasida (Piroplasmea) order Piroplasmida families Babesiidae and Theileriidae;

absence of a preerythrocytic cycle in Babesia and the absenceof transovarial transmission in Theileria.

Initially, Babesia species identified - morphological

parameters of the intraerythrocytic forms (i.e., trophozoites) This analysis, along with host specificity, has provided

> 100 species of Babesia 7 spp. affect humans

Large(2.5-5m) Transovarial

Small (1.02.5m) Transstadial

Babesiosis, HOMER et.al. CMR, July 2000, p. 451469

Structure

Lifecycle

Reservoir White tailed deer

For all except B. meri ornithodorrus

EpidemiologyWA-1 B. microti 300 cases

B. divergens

Temperate climates

Epidemiology Frequency of B. microti & WA-1 in US > reported cases

because self- limiting & mild in humans

Mortality in USA 5% Survey in California 16% prevalence WA-1 Survey of Blood donors - 3-8% prevalence B. microti

Human cases of B. microti reportedCoastal areas of southern New England Eastern Long Island Minnesota Winsconsin

WA-1 throughout pacific coastsBabesiosis, HOMER et.al. CMR, July 2000, p. 451469

Contd.. Sporadic cases Europe (France & British Isles),

Africa, Asia Cattle Babesia (B. divergens, B. microti)

83% Babesiosis in Europe - B. divergens

Mortality rate 42% Europe Few cases reported China, Taiwan, Egypt, S. Africa,

Mexico Transfusion- acquired Babesia several cases in USA, but none in Europe & elsewhere

India Single case report 51 year old patient from Madhya Pradesh History Working nursing home in gwalior Fever, vomiting, headache, arthralgia No h/o tick bite or visit to endemic area No other family member No h/o splenectomy or blood transfusionIJMM 2005;23:267-9

O/E Liver and spleen palpable Scleral icterus, passed dark coloured urine Investigations WBC count 1,900/cumm Platelet count 55,000/cumm LDH raised

Peripheral blood smear ring forms varied greatly

confused P. Falciparum Antimalarial treatment no response Smear reviewed pear shaped, tetrad - babesiosis suspected HRP II negative Quinine + clindamycin Pt. afebrile within 2 days

PathogenesisEnv

HostAgent

Modification and rupture of RBCs

Replication neoAg`s d/t membrane alteration

Docking sites for IgG and complement phagocytosis in spleen Anemia

Lack of periodicity: Asynchronous replication More severe manifestations in immunosuppresed and

elderly

establishment stage antibodies (IgG) play a role in

preventing erythrocyte infection by binding the free sporozoites. progression stage organisms invade erythrocyte innate immune system control growth rate of the merozoites NK cells and macrophages - soluble factors: IFN-g by NK

cells and TNF-a, nitric oxide (NO), and ROSs by macrophages (Mf).

resolution stage decrease in parasite numbers -

intracellular degeneration inside the erythrocyte, as evidenced by the appearance of crisis forms.

Clinical features Disease manifestations asexual reproductive stage Predisposing factors +/ Mild to severe illness Generalized weakness

Fever Gastrointestinal symptoms (anorexia, nausea, abdominal pain, vomiting, diarrhea,

etc.) Headache Myalgia Weight loss Arthralgia Respiratory symptoms (cough, shortness of breath, etc.) Dark urine

Clinical examination Hepatomegaly and splenomegaly Hemolytic anemia - lasts from several days to few

months occur in clinically severe cases, most commonly in asplenic or elderly

Pulmonary manifestations - rare in babesiosis, but

non-cardiogenic pulmonary edema (NCPE) is the most frequent manifestation not related degree of parasitemia splenic function and its onset may be early or late

16 reported cases - reviewing the literature on the

pulmonary complications

Common Complications Acute respiratory distress syndrome Anemia requiring transfusion Congestive heart failure Disseminated intravascular coagulation Hypotension/shock Myocardial infarction Renal failure

HUMAN COINFECTION Coinfection with B. microti & other tick-borne

pathogens, particularly B. burgdorferi (Lymes disease)

serosurveys - 13% of Lyme disease patients in babesia-endemic areas are coinfected with B. microti

B. microti is transmitted by the same Ixodes tick that

perpetuates the agents ofLyme disease human granulocytic ehrlichiosis novel Bartonella species

P. leucopus is also the vertebrate reservoir for at least

three of the known pathogens

Patients coinfected with B. microti and B. burgdorferi

experience

more severe symptoms, resulting in fatality in rare cases persistence of postinfectious fatigue.

B. burgdorferi DNA persisted for prolonged periods B. microti - no significant effect on the duration of

parasitemia

Blood transfusion

Travel history Clinical presentation

Splenectomy

Diagnosis

Tick bite

Age

A positive Coombs test in combination with hemolytic

anemia & elevated procalcitonin levels is highly suspicious of babesiosis Laboratory tests examination of stained blood smears serologic evaluation with indirect (immuno) fluorescent

antibody tests (IFATs) PCR

Examination of thin blood

smears most frequently used technique Wrights or Giemsa stain simple rings (annular), pear-shaped (pyriform), Maltese cross (tetrad form) High parasitemia present during

acute infections

varying from 5 to 80% of erythrocytes

Duration of detectable parasitemia on blood smears

varies

3 weeks to 12 weeks with the longest duration of smear positivity being 7 months for a splenectomized patient

Quantitative buffy coat system (QBC) Merozoites

stained with acridine orange

Simple & rapid Showed 100% correlation with blood smear exam. (Mattia et al, 1993)

Distinguishing features differentiate the two

organisms. Babesial organisms usually form tetrads ("Maltese

cross"), Do not have hemozoin pigments within the affected red blood cells Have extracellular merozoites

Serodiagnosis IFATs - B. microti infections, chronic infections

Hamster-derived B. microti Ag Distinguish between B. microti, WA-1, B. divergens Specific and sensitive Diagnostic titers above 1:64 Higher cutoff titers (1:128 to 1:256) greater diagnostic specificity IgM and IgG Problematic in HIV, splenectomy Time consuming & labor intensive

IFAT Antibody titers can remain elevated for as long as 13

months to 6 years after infection Although persistence of antibody does not necessarily reflect a measurable infection, levels of IgG antibody decline less rapidly in persistently infected patients

ELISA ELISA Recombinant antigen - 4 antigens used

rBMN1-2 rBMN1-15 rBMN1-17 rMN-10

- 27/40 - 27/40 - 27/40 - 27/40

Showed high sensitivity & specificity Soluble whole parasite antigen (B. divergens)

Loades et al, 2000

Problem associated with serological tests

Relationship between antibody titers, the presence of parasites, and the state of protective immunity is not clear

Antibodies may persist for long periods after the disease has cleared

Overestimate of disease prevalence

Antibody titers may be observed in the absence of protectiveimmunity

PCR assay Based on universal primer amplification of a fragment

of the small subunit rRNA gene Highly conserved among babesias Heterologous between Babesia spp. and other intraerythrocytic protozoal parasites as well as within the genus Babesia itself Distinguishes readily between B. divergens, B. microti, and Plasmodium spp., it provides a valuable adjunctive

Advantages over IFA testing. Less time consuming conducted by generalist technicians more readily be standardized sensitivity and specificity comparable to those of conventional IFAs

MASP(microaerophilous stationary phase) culture technique

Quantities of parasite nucleic acid needed for defining phylogenetic relationships of these species,

Methods for detection of the parasite in otherwise

asymptomatic individuals

Producing parasite antigens Attenuated strains of Babesia - immunization.

Laboratory diagnosis B. microti immunoblot kits Animal Inoculation

2-4 weeks Sensitive (300 org./ml blood) Time consuming, expensive

Animal models Rats

BALB/ c mice Splenectomized calves Gerbils

Treatment

Imidocarb and the combination of oxomemazine and

phenamidine were most effective in vitro Imidocarb, although not licensed for human use, most

effective agent for treating B. divergens infections in cattle other pharmacologic interventions - chloroquine,

tetracycline, primaquine, sulfadiazine, andpyrimethamine

Prevention Avoidance of or minimization of exposure to tick

infested areas Ase of tick repellents before entering a tick-infested area thorough examination of skin after exposure. Ticks found before attachment -removed, and Ticks found after attachment removed within 24 h limit the possibility of transmission Application of pesticide to host nests and on the coats of reservoir hosts can interrupt transmission

Vaccines Live vaccines

living parasites cattle B. bovis & B. bigemina vaccine cattle Soluble parasite antigen (SPA) No effective B. microti vaccine MRA gene (Maltase cross form-related antigen) 37 kDa glycoprotein (Bd37)

Recombinant vaccines

Human vaccines Expt. Stage

Summary Emerging disease Common in the Americas Can be confused with plasmodium falciparum

infection Diagnosis requires high index of suspicion Treatment involves use of At or Az or Clin + Quin

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